Field of the Invention
This invention relates to a process and an apparatus for producing zirconium sponges by reducing zirconium halide with a reducing agent such as magnesium, sodium, and the like.
Processes and apparatus for commercially producing zirconium sponge have already been proposed wherein purified dense or powder zirconium tetrachloride and magnesium (or sodium) are placed at one time into a reaction chamber and heated at an elevated temperature in the presence of an inert gas such as argon to be vaporized and then reduced with the magnesium (or sodium). The inert gas is introduced in the reaction chamber in such a way that the internal pressure of the reaction chamber is held slightly higher than the atomospheric pressure for the purposes of preventing the reduction from rapidly proceeding to raise the temperature and preventing even trace amount of nitrogen and oxigen from having an undesirable effect on the produced zirconium sponge. However, such prior processes and apparatus have had numerous disadvantages as follows:
(1) The reaction chamber itself is required to have a considerably wide space for receiving the purified dense or powder zirconium tetrachloride which is previously placed therein, and the volume of the produced zirconium sponge is less than approximately one-eighth of that of the reaction chamber since only one reaction is possible in every batch.
(2) The zirconium tetrachloride is reacted in the gas state with the magnesium, and therefore a great amount of heating energy is required to vaporize the zirconium tetrachloride at an elevated temperature.
(3) The internal pressure of the reaction chamber, which increases as temperatures get higher, is ordinally adjusted by discharging the inert gas from the reaction chamber so as to maintain the pressure slightly higher than atomospheric pressure. At this time, some zirconium tetrachloride gas is discharged along with the inert gas so as to be wasted and so as to condense and adhere to portions such as a valve whose temperature is relatively low (below 331.degree. C), resulting in blockade of pipes or the like.
(4) It is very difficult and requires special training or skill to properly control the discharge of the inert gas since the inert gas is randomly mixed with the zirconium tetrachloride gas. Therefore, the inert gas is sometimes discharged above the proper amount and the zirconium tetrachloride gas is excessively concentrated within the reaction chamber so that the reduction proceeds more rapidly than is normally the case and a great amount of formation heat applies to the reaction chamber. Although the reaction chamber is made of a heat-resisting metal, when the reaction chamber is heated above 935.degree. C, eutectic taking place between Fe and Zr to form a Fe -- Zr alloy has a direct effect upon the reaction chamber, thereby deteriorating the quality of the produced zirconium sponge. Conversely, the inert gas is sometimes discharged below the proper amount so that the reduction proceeds slowly and requires extremely long reduction times, which is disadvantageous in economy.
Further, in the prior processes and apparatus, the zirconium tetrachloride is vaporized and the reduction is carried out by reacting zirconium tetrachloride gas on the magnesium and not directly on the solid zirconium tetrachloride. No commercial attenmpt has been proposed in the art wherein solid zirconium tetrachloride is directly reacted with magnesium for the reason that it is difficult to produce powder zirconium tetrachloride free from impurities, such as oxygen, which have an undesirable effect upon the quality of the produced zirconium sponge. Also, no commercial attempt has been proposed in the art wherein solid zirconium tetrachloride is directly supplied in a reaction amount to a reaction chamber which has been heated to an elevated temperature. The reason for this is that zirconium tetrachloride sublimes at 331.degree. C and if the chamber is at an elevated temperature when the zirconium tetrachloride is supplied thereto, the zirconium tetrachloride gas would flow from the reaction chamber into the supply means, condensing and adhering on certain portions thereof, resulting in blockade of the supply means.
This invention further relates to an apparatus for producing metallic zirconium by vacuum separation processes without cooling the product obtained from the reduction of the halogenated zirconium with magnesium or sodium.
In the hitherto used apparatus for producing metallic zirconium, a condenser means for vacuum separation of the reduced product is independent of the reaction chamber wherein the zirconium halide is reduced. Therefore the vacuum distillation process cannot be carried out before the product is cooled and conveyed from the reaction chamber into the condenser means. Accordingly, many disadvantages have been found in such prior apparatus such as:
(1) A great amount of heating energy is required for a relatively long time to reheat the once cooled product up to an elevated temperature.
(2) The reduced by-products which is the zirconium sub chlorides and the magnesium chloride is exposed to the air resulting in absorbing moisture, thereby deteriorating the quality of the zirconium sponge.
(3) In conveying the reduced product from the reaction chamber to the condenser means for vacuum separation, the zirconium sub chlorides decomposes to exhaust a harmful gas in the air. Further, the moisture absorption of the magnesium chloride cause the generation of hydrogen chloride in the initial degassing stage, which results in breakage of the vacuum pump.